Kohler 20--2800 kW manual Auxiliary Fuel Pumps

6.5 Auxiliary Fuel Pumps

Engine-driven fuel transfer pumps usually develop a maximum of 7 psi (48 kPa) pressure and have a lift capacity of 4-6 feet (1.2-1.8 m). Even if the engine pump can draw fuel a greater distance, a more reliable system results if a transfer tank and/or auxiliary pump are used when the vertical lift exceeds three feet or fuel must be drawn horizontally more than 20 feet (6.1 m).

On engines using less than ten gallons (38 L) of fuel per hour (approximately 100 kW or less), an electric fuel transfer pump powered by the engine starting battery can be installed in series with the engine-driven transfer pump. Best results are obtained when the electric pump is located near the fuel tank rather than near the engine.

Where fuel must be lifted 6 feet (1.8 m) or more, or long horizontal runs are involved, an electric motor driven positive displacement pump should be used with a transfer tank and float switch. The power supply for the

pump should always be from the load side of the transfer switch for maximum reliability. Such pumps typically are capable of lifting fuel 18 feet (5.5 m) or drawing it horizontally up to 200 feet (61 m).

Where vertical or horizontal runs exceed these limits, the pump should be remote mounted adjacent to the fuel storage tank. When so located, these pumps can push fuel over 1,000 feet (305 m) horizontally or more than 100 feet (30.5 m) vertically and deliver adequate fuel for generator sets up to 2800 kW. Positive displacement pumps should never be connected directly to an engine; a transfer tank and float switch should always be used so the engine fuel system is not subjected to excessive fuel pressures.

A check valve or shutoff solenoid valve (wired into the engine ignition) can be used to help keep the fuel line primed. If such a valve is included in the system, it should be installed on the outlet side of the auxiliary fuel pump to minimize inlet restriction.

28 Section 6 Fuel Systems TP-5700 7/93